The protein Akt, also known as Protein Kinase B, regulates fundamental processes like cell growth, proliferation, and metabolism. When the Akt signaling pathway is dysregulated, it can contribute to the development of diseases, including cancer and metabolic disorders. Like all proteins, Akt possesses a distinct molecular size and weight. Understanding these properties allows for its identification and characterization in biological research.
How Protein Size is Measured
Proteins are large molecules constructed from building blocks called amino acids. A protein’s size is described by its molecular weight, representing the combined mass of all atoms in the molecule. The standard unit is the Dalton (Da), but because proteins are large, their mass is expressed in kilodaltons (kDa), where one kilodalton equals 1,000 Daltons.
A protein’s molecular weight is directly related to the number of amino acids it contains. On average, a single amino acid has a molecular weight of approximately 110 Daltons. This allows for an estimation of a protein’s size from its amino acid count; for example, a protein with 500 amino acids has an approximate molecular weight of 55 kDa.
Dimensions of Akt Protein Isoforms
In humans, Akt exists as a family of three distinct proteins known as isoforms: Akt1, Akt2, and Akt3. These isoforms share a high degree of similarity but are encoded by different genes. This genetic distinction results in slight variations in their amino acid sequences, which leads to small differences in their molecular weight.
The calculated molecular weight for human Akt1 is approximately 56 kDa (480 amino acids), while Akt2 is very similar at 56.1 kDa (481 amino acids). The Akt3 isoform has a calculated weight of around 55.8 kDa (479 amino acids). However, it often appears larger in experiments, in the 59-62 kDa range.
Practical Importance of Akt’s Size
The molecular weight of each Akt isoform is important in biomedical research. It serves as a primary identifier in the Western blot, a common technique that separates proteins based on size. An electrical current pulls proteins through a gel matrix, and by comparing the protein bands to a molecular weight ladder, researchers can identify the Akt isoforms, which appear around the 56-62 kDa mark.
The apparent size of Akt can also indicate its activity state. A post-translational modification called phosphorylation activates Akt by adding phosphate groups. This addition increases the protein’s mass, causing it to appear as a slightly heavier band (around 60 kDa) on a Western blot. This size shift is a valuable indicator for scientists studying cellular signaling.